df1: 
   name     job       id_number  Salary
0  krul                125796    45000
1  arnold   lawyer     789632    25000
2  daisy    engg       256498    
3  alex                456985    65884
4  mandy    arch       456258    36958
5  krul     painter    
6  perry               789632 
7  timu     lawyer     
8  timy     lawyer     789632    69822
9  daisy    engg       
10 daisy    engg       256498    54869


df2:
ColumnName  allow_null
  name       True
  job        True
  id_number  False
  Salary     True

我想检查df1中每列的缺失值总和，并替换为该列的均值或众数。

如果该列是df2中提到的不可为null的列（allow_null == False），则引发错误，是否根据列数据类型将其替换为均值或众数？